need input on toroidial dishes

[spacebug42]

I'm still in the process of engineering a work-around on my C/Ku band project in regards to how I would be able to connect it to the whole house TV network. It looks as if I might have to put a 2 x 1 switch in and just dedicate the switch's output to only the living room. This brought about the question on how I will connect the satellite dish to the 5 x 8 Multi-switch. Somehow I had stumbled across a couple of links on the Sadoun's web site for a Toroidial dish (T55 and T90).

If you're not familiar with a toroidial dish, it operates a bit differently than offset dishes. It uses two reflection paths - one from the satellites and one to reflect into the LNBFs. The LNBFs are installed on a curved bracket which allows the installer to install up to 5 LNBFs and adjust the skew for each one.

I am very curious to know if anybody has or is using one at their home and how well it works for you. The toroidial dish seems like it will solve my rain fade problem and also offers reception of multi-satellites within a 40 degree range without a motor. I like the idea of using it to pick up 83 (RTN), 97 & 101 (GloryStar), and possibly 119 (NASA, ION, and Angel One), but I want to hear from others how well it works for them before I spend money for it.

 

[spacebug42]

my apology for getting too excited

Apparently, I was filling up with excitement about using a toroidal dish until I had done some research on Google. There's a major drawback to using these dishes. There had been a warning posted here about this type of dish. You can read it here. http://www.satelliteguys.us/free-air-fta-discussion/14693-toroidal-dishes-warning.html. I did find the link on the Sadoun web site for this dish. Toroidal Dishes Antennas Wave Frontier Multi LNBF. It does say on Sadoun's web site that the T55 cannot be used for FTA purposes, but the T90 can be used for that purpose.

After reading the warning and seeing the fine print on the use of toroidial dishes, I'm not going to pursue that idea. I'm now thinking about using a 1.2m dish with a multi-LNB bracket. I'd like to modify the question and direct it to those who use a 1.2m dish with a multi-LNB bracket. How well does it work for you?

 

[pendragon]

I'm quite fond of my T-90s - I've bought three of them. When I'm done messing around I'm planning on posting this and other details of my system, but suffice it to say I have at last count 27 LNBs running from 61.5W to 139W. The full coverage is about 58W to 148W. I've published a number of dish performance measurements and LNB comparisons in threads over the past year.

If you've never worked with a toroid before, it takes a little more tweaking than an ordinary Ku-band dish, but the dish adjustments are easily done and the mount is solid on the T-90s. There is a little loss going off-axis, but one simply can't compare this to the much larger losses one has on other dish geometries. I can be a real perfectionist, so I keep FSS birds not more than 12-15 degrees off-axis. DBS birds generally have higher power and there doesn't seem to be a problem running those out to 20 degrees off-axis or even a little farther.

One easily overlooked twist about dual reflectors like the T-90 is they cause circularly polarized signals like from 119W to be reversed compared to a single refelector. You can get LNBFs from Wave Frontier and I believe Sadoun to handle this if you want, but you can also modify a DN LNBF very easily or just ignore it, as for legal FTA uses of 119W it doesn't really matter. If you order a T-90 from Wave Frontier, you can save some dosh by asking them to omit the LNBFs that are normally included.

 

[pendragon]

After reading the warning and seeing the fine print on the use of toroidial dishes, I'm not going to pursue that idea. I'm now thinking about using a 1.2m dish with a multi-LNB bracket. I'd like to modify the question and direct it to those who use a 1.2m dish with a multi-LNB bracket. How well does it work for you?

I think you let the pendulum swing too far the other way. A T-55 is roughly equivalent to a 20" DTV or DN dish. No knowledgeable person here would recommend any 20" dish for FTA purposes, and the T-55 is no exception. That is the basic message the poster is warning about. The T-90 is a much different animal and has the gain of a typical 90cm Ku dish, which is more than enough for most purposes and is a lot better than the 33" dish recommended by the poster. I found the poster's other remarks to be somewhat emotional and dubious:

1. Dual reflectors and circularly polarized signals - reversed circular LNBFs are only slightly more expensive than regular ones. But unless you're using your toroid to mount LNBs for a DTV, DN or even Bell subscription receiver you don't need such a critter. Your FTA receiver only knows H & V polarizations. It makes no difference if you translate these to L & R or R & L. If you have a subscription receiver, you could buy a reversed LNBF or modify an existing one. I pulled the cap off my DN DishPro LNBFs, rotated the dielectric plate 90 degrees, put the cap back on and had the thing running in a couple of minutes. Linear satellites don't need any special treatment - ordinary linear LNBs work fine on a toroid.

2. Setting the LNB spacing on a T-90 is absolutely trivial. There's a rail along which the LNBs slide. You move it left or right to tune and tighten the set screw. This is much easier than messing around with multi-LNB brackets.

3. Two degree spacing - this is essentially impossible to do on a standard fixed Ku-dish. It's still a little hard on a T-90, but the rail and the very wide main reflector spreads out the orbital spacing very nicely. You also get more rejection from adjacent satellites than on a typical offset dish. Four degree spacing is child's play on a T-90, whereas this is not easy on a normal Ku dish.

4. By forgoing the unnecessary LNBFs, I paid $120 for each T-90 plus shipping. That's a pretty fair price in my book for what this dish can do. I paid a little more for a 1.2m offset, about the same shipping, and another $100 for a motor. The 1.2m has more gain, but is a lot less useful at 50% higher cost.

I bought my 1.2m/motor before the T-90s. Even with its higher gain there's hardly anything that only it can get. It now sits for weeks at a time unused, while the T-90s handle all our Ku viewing. It's nice not to have to move the dish back and forth, and coordinate its use across multiple receivers.

I picked up a multi-LNB bracket for fun along the way and tried it on the 1.2m. After about 3-4 degrees off-axis, its gain is less than the T-90s (see attached plot from an earlier thread of mine). This is a physical limitation of a parabolic dish. If you only wanted 97W and 101W, a 1.2m would probably do the job. But you're unlikely to get 119W at 20 degrees off center and no way will you get 83W. That far off-axis a 1.2m offset is going to behave worse than a 20" pizza dish.

 

[Mr Tony]

my review of the T90
http://www.satelliteguys.us/fta-mpe...ve-frontier-toroidal-t-90-satellite-dish.html

and when I had 2 degree spacing on it
Finally got the T90 dish back up...now with 2 degree spacing - SatelliteGuys.US

 

[updatelee]

I first had a T55 then gave it to a friend and bought a T90, I then sold him the T90 and went back to my 1m motor.

they claim 40deg of arc but you can stretch it farther if you want, I found a T55 was equal to something around a 24" in the center and degraded to something around a 12" on the edges of the 40deg arc. yes read that correctly.

the T90 was equal to a cheap poorly made 30" in the center, and about an 18" on the edge of the arc.

I was really disapointed, if your looking for something to receive circular signals on a large arc then consider it, if your true to fta then I dont really see how its of much use. Im a signal hound and expect my equipment to perform exceptionally, not mediocre.

I can receive bev 91 on a 12" aluminum pie crust foil, but I dont. It may be neet to play with just to see if you can do it, but its not worth using as your main reflector.

note: just my opinion, lots of guys love them, including my friend I sold mine to. just not for me.

 

[spacebug42]

thanks for the info

Thanks guys for your helpful information. Pendragon, I know 83 is a weak bird, but it wouldn't hurt to at least try. When I first started getting into FTA, all I had was the receiver's SQ meter. Two months ago, I bought a used BirDog meter on eBay and already made my realignment of the dish very quick - done in less than five minutes. Since that tweaking of the dish, I get strong signals from 72 to 129. I need to see if I can tweak the azimuth so that the q will be higher. I enjoy technical challenges and I look forward to trying on this one. Ice, I read your two reviews and I liked what you shared on what you went through to assemble, install and align the LNBs to pick up the birds. Updatelee, I didn't like the way you tried to dampen my spirits. I was thrown off or should I say am confused as to how Ice was able to pick up everything within a 50 degree when the maximum limit is 40 degrees. When they say 40 degrees, does that refer to 40 degrees on each side of the 0 mark or is it 20 degrees on each side of the 0 mark?

 

[Mr Tony]

its 40 degrees total....so I had originally 72-111.1 which is close to 40 degrees. Its 20 degrees on either side of 0

I added a piece of wood for 119. SInce its DBS I could afford the lower signal.

I loved my T90 and the signals on the T90 even at the ends were the same as the middle so I dont know where lee got that info. This is when 74W was the "king" of sports feeds sats and I had no issues getting the feeds off 74W. My centre LNB was 91 or 93

 

[updatelee]

both my torodials were wavefrontier's not generic clones either.

many are happy with them, I wasnt. Im much happier with a motor and dish. unless you have a specific need for a torodial (ie youve got multiple ird's that need to tune multiple satellites all at the same time) you'll get better signal and larger arc from a motor, as long as everyone in the house can live with watching programming on the same satellite.

 

[pendragon]

the T90 was equal to a cheap poorly made 30" in the center, and about an 18" on the edge of the arc.

I'm not sure what caused this other than perhaps alignment. I measured my T-90 against my GeosatPro 1.2m on the spectrum analyzer and using some calibrated PC tuners. A 1.2m should outperform a 90cm by about 2.5 dB theoretically, and the difference was less than that at the center of the T-90. On top of this the T-90 had nearly the same adjacent orbital location rejection as the 1.2m, probably because it is so wide. I have some well made 76cm (30") dishes that I now only use for my DN subscription. The T-90 blows them away, even at the extremes of its range.

I don't have a problem with motors and when I'm copying a critical high-SR feed I still steer the 1.2m over to it. But I get everything on the toroids with good margins, whether it is RTV on 83W, NBC on 103W (custom skew of course), LPBS on 125W, you name it.

 

[updatelee]

Well I have a satllook spectrum analyzer as well, its a great tool. But my results were less then steller.

If youve got the money to spend on trying new things out, they really are a neet little unit to play with. They even come up used once in awhile for cheaper. There is a guy locally right now trying to sell a T90 for $150cdn inc 12 lnbs and brackets.

I just found for me it wasnt something I was going to use for day to day because the performance just wasnt there.

 

[Wescopc]

I love my T-90, I went through 2 motors and decided to try the T-90... don't have to fiddle with it like I did the motors.
Bob

 

[pedrogarcia]

I prefer the T90 to a motor system, I think it is a far better performer but it does have some quirks. It is infinately touchy on adjustment, no good for circular, but great for the odd skew problem. I would not recommend it to a newbie or someone without a Sat Analyser. I am sure guys have used it without a SA and those of you who have, must have lots of patience.

 

[Mr Tony]

I dont have a SA and I had no issues
but then again, my true south was my middle LNB so the skew was 0

 

[pendragon]

I've set up all three of my T-90s with just a signal squawker, although with one I did spot check some CNRs using a PC tuner. Of course once each was aligned I couldn't keep from running the SA on them. I don't have a portable SA and while I can remote my bench unit through a wirelessly-networked laptop, that isn't all that much fun on the roof where most of our dishes are mounted. The best advice I can offer is to initially set up the dish for the center position, and then do the fine alignment only with LNBs positioned roughly the same distance off-axis at the most extreme ends of the rails.

In terms of circular polarization, it takes me about two minutes to convert a DishPro LNBF to the reversed format. Of course one can simply just buy reversed one for about $20. On one of my toroids I have a converted LNB pointed at 77W (2 degrees off-axis) and another one at 61.5W (17.5 degrees off-axis). Both work fine with our DN subscription receivers, although we prefer the western arc birds. I haven't seen any obvious problems with cross-polarization, and the performance is better than on standard-issue 76cm offsets. The only reason I haven't moved the DN western arc LNBs off our 76cm dishes onto the toroids is the latter tend to accumulate wet, heavy snow and I'm sometimes too lazy to climb on the roof to knock it off.

 

[pedrogarcia]

I dont have a SA and I had no issues
but then again, my true south was my middle LNB so the skew was 0

Yes but you and Pendragon are super expert status